In connection with the operation of coal-fired furnaces which are used in vapor generating systems in the utility industries for the production of electricity, it is necessary to supply finely powdered coal to the combustion chamber of the furnace. The raw coal feedstock is usually reduced to comminuted particles in a pulverizing apparatus which generally consists of a housing in which is located a rotating grinding table having a grinding ring, and in which relatively heavy rollers are journaled and maintained in contact with the material on the grinding ring.
Various arrangements of pulverizing apparatuses have been used in the past. For example, there have been pulverizers consisting of a plurality of rollers over which a thrust ring was located which applied a downward load to the rollers which would travel in a planetary manner. In such a design the rollers would tend to skid at the point where the pressure ring contacted the roller. Additionally, the ring and rollers would wear as a result of the contact between them.
In another design the rollers were attached to an upper pressure transmitting ring which allowed for vertical movement of the rollers, but did not allow for lateral movement. Such a design subjected the rollers and upper ring to severe stress from vibration.
In a further known design the rollers were attached to an upper pressure transmitting ring which allowed for vertical as well as lateral movement of the rollers by mounting the roller axles on suspension members fulcrumed on the pressure transmitting ring. Such a design restricted the capability of the roller to move around any accumulation of material to be ground since only lateral or vertical movement was provided for.